package com.fsck.k9.mail.store.imap

import com.fsck.k9.logging.Timber
import com.fsck.k9.mail.Body
import com.fsck.k9.mail.BodyFactory
import com.fsck.k9.mail.FetchProfile
import com.fsck.k9.mail.Flag
import com.fsck.k9.mail.K9MailLib
import com.fsck.k9.mail.Message
import com.fsck.k9.mail.MessageRetrievalListener
import com.fsck.k9.mail.MessagingException
import com.fsck.k9.mail.Part
import com.fsck.k9.mail.filter.EOLConvertingOutputStream
import com.fsck.k9.mail.internet.MimeBodyPart
import com.fsck.k9.mail.internet.MimeHeader
import com.fsck.k9.mail.internet.MimeMessageHelper
import com.fsck.k9.mail.internet.MimeMultipart
import com.fsck.k9.mail.internet.MimeParameterEncoder.isToken
import com.fsck.k9.mail.internet.MimeParameterEncoder.quotedUtf8
import com.fsck.k9.mail.internet.MimeUtility
import java.io.IOException
import java.io.InputStream
import java.text.SimpleDateFormat
import java.util.Date
import java.util.Locale
import kotlin.math.max
import kotlin.math.min

internal class RealImapFolder(
    private val internalImapStore: InternalImapStore,
    private val connectionManager: ImapConnectionManager,
    override val serverId: String,
    private val folderNameCodec: FolderNameCodec,
) : ImapFolder {
    private var uidNext = -1L
    internal var connection: ImapConnection? = null
        private set
    private var exists = false
    private var inSearch = false
    private var canCreateKeywords = false
    private var uidValidity: Long? = null

    override var messageCount = -1
        private set

    override var mode: OpenMode? = null
        private set

    val isOpen: Boolean
        get() = connection != null

    override fun getUidValidity(): Long? {
        check(isOpen) { "ImapFolder needs to be open" }
        return uidValidity
    }

    @get:Throws(MessagingException::class)
    private val prefixedName: String
        get() {
            var prefixedName = ""
            if (!INBOX.equals(serverId, ignoreCase = true)) {
                val connection = synchronized(this) {
                    this.connection ?: connectionManager.getConnection()
                }

                try {
                    connection.open()
                } catch (ioe: IOException) {
                    throw MessagingException("Unable to get IMAP prefix", ioe)
                } finally {
                    if (this.connection == null) {
                        connectionManager.releaseConnection(connection)
                    }
                }
                prefixedName = internalImapStore.getCombinedPrefix()
            }
            prefixedName += serverId

            return prefixedName
        }

    @Throws(MessagingException::class, IOException::class)
    private fun executeSimpleCommand(command: String): List<ImapResponse> {
        return handleUntaggedResponses(connection!!.executeSimpleCommand(command))
    }

    @Throws(MessagingException::class)
    override fun open(mode: OpenMode) {
        internalOpen(mode)

        if (messageCount == -1) {
            throw MessagingException("Did not find message count during open")
        }
    }

    @Throws(MessagingException::class)
    private fun internalOpen(mode: OpenMode): List<ImapResponse> {
        if (isOpen && this.mode == mode) {
            // Make sure the connection is valid. If it's not we'll close it down and continue on to get a new one.
            try {
                return executeSimpleCommand(Commands.NOOP)
            } catch (ioe: IOException) {
                /* don't throw */
                ioExceptionHandler(connection, ioe)
            }
        }

        connectionManager.releaseConnection(connection)

        synchronized(this) {
            connection = connectionManager.getConnection()
        }

        try {
            val openCommand = if (mode == OpenMode.READ_WRITE) "SELECT" else "EXAMINE"
            val encodedFolderName = folderNameCodec.encode(prefixedName)
            val escapedFolderName = ImapUtility.encodeString(encodedFolderName)
            val command = String.format("%s %s", openCommand, escapedFolderName)
            val responses = executeSimpleCommand(command)

            /*
             * If the command succeeds we expect the folder has been opened read-write unless we
             * are notified otherwise in the responses.
             */
            this.mode = mode

            for (response in responses) {
                extractUidValidity(response)
                handlePermanentFlags(response)
            }

            handleSelectOrExamineOkResponse(ImapUtility.getLastResponse(responses))

            exists = true

            return responses
        } catch (ioe: IOException) {
            throw ioExceptionHandler(connection, ioe)
        } catch (me: MessagingException) {
            Timber.e(me, "Unable to open connection for %s", logId)
            throw me
        }
    }

    private fun extractUidValidity(response: ImapResponse) {
        val uidValidityResponse = UidValidityResponse.parse(response)
        if (uidValidityResponse != null) {
            uidValidity = uidValidityResponse.uidValidity
        }
    }

    private fun handlePermanentFlags(response: ImapResponse) {
        val permanentFlagsResponse = PermanentFlagsResponse.parse(response) ?: return

        val permanentFlags = internalImapStore.getPermanentFlagsIndex()
        permanentFlags.addAll(permanentFlagsResponse.flags)
        canCreateKeywords = permanentFlagsResponse.canCreateKeywords()
    }

    private fun handleSelectOrExamineOkResponse(response: ImapResponse) {
        val selectOrExamineResponse = SelectOrExamineResponse.parse(response) ?: return // This shouldn't happen
        if (selectOrExamineResponse.hasOpenMode()) {
            mode = selectOrExamineResponse.openMode
        }
    }

    override fun close() {
        messageCount = -1

        if (!isOpen) {
            return
        }

        synchronized(this) {
            // If we are mid-search and we get a close request, we gotta trash the connection.
            if (inSearch && connection != null) {
                Timber.i("IMAP search was aborted, shutting down connection.")
                connection!!.close()
            } else {
                connectionManager.releaseConnection(connection)
            }

            connection = null
        }
    }

    @Throws(MessagingException::class)
    private fun exists(escapedFolderName: String): Boolean {
        return try {
            // Since we don't care about RECENT, we'll use that for the check, because we're checking
            // a folder other than ourself, and don't want any untagged responses to cause a change
            // in our own fields
            connection!!.executeSimpleCommand(String.format("STATUS %s (RECENT)", escapedFolderName))

            true
        } catch (ioe: IOException) {
            throw ioExceptionHandler(connection, ioe)
        } catch (e: NegativeImapResponseException) {
            false
        }
    }

    @Throws(MessagingException::class)
    override fun exists(): Boolean {
        if (exists) {
            return true
        }

        /*
         * This method needs to operate in the unselected mode as well as the selected mode
         * so we must get the connection ourselves if it's not there. We are specifically
         * not calling checkOpen() since we don't care if the folder is open.
         */
        val connection = synchronized(this) {
            this.connection ?: connectionManager.getConnection()
        }

        return try {
            val encodedFolderName = folderNameCodec.encode(prefixedName)
            val escapedFolderName = ImapUtility.encodeString(encodedFolderName)
            connection.executeSimpleCommand(String.format("STATUS %s (UIDVALIDITY)", escapedFolderName))

            exists = true

            true
        } catch (e: NegativeImapResponseException) {
            false
        } catch (ioe: IOException) {
            throw ioExceptionHandler(connection, ioe)
        } finally {
            if (this.connection == null) {
                connectionManager.releaseConnection(connection)
            }
        }
    }

    @Throws(MessagingException::class)
    fun create(): Boolean {
        /*
         * This method needs to operate in the unselected mode as well as the selected mode
         * so we must get the connection ourselves if it's not there. We are specifically
         * not calling checkOpen() since we don't care if the folder is open.
         */
        val connection = synchronized(this) {
            this.connection ?: connectionManager.getConnection()
        }

        return try {
            val encodedFolderName = folderNameCodec.encode(prefixedName)
            val escapedFolderName = ImapUtility.encodeString(encodedFolderName)
            connection.executeSimpleCommand(String.format("CREATE %s", escapedFolderName))

            true
        } catch (e: NegativeImapResponseException) {
            false
        } catch (ioe: IOException) {
            throw ioExceptionHandler(this.connection, ioe)
        } finally {
            if (this.connection == null) {
                connectionManager.releaseConnection(connection)
            }
        }
    }

    /**
     * Copies the given messages to the specified folder.
     *
     * **Note:**
     * Only the UIDs of the given [ImapMessage] instances are used. It is assumed that all
     * UIDs represent valid messages in this folder.
     *
     * @param messages The messages to copy to the specified folder.
     * @param folder The name of the target folder.
     *
     * @return The mapping of original message UIDs to the new server UIDs.
     */
    @Throws(MessagingException::class)
    override fun copyMessages(messages: List<ImapMessage>, folder: ImapFolder): Map<String, String>? {
        require(folder is RealImapFolder) { "'folder' needs to be a RealImapFolder instance" }

        if (messages.isEmpty()) {
            return null
        }

        checkOpen() // only need READ access

        val uids = messages.map { it.uid.toLong() }.toSet()
        val encodedDestinationFolderName = folderNameCodec.encode(folder.prefixedName)
        val escapedDestinationFolderName = ImapUtility.encodeString(encodedDestinationFolderName)

        // TODO: Just perform the operation and only check for existence of the folder if the operation fails.
        if (!exists(escapedDestinationFolderName)) {
            if (K9MailLib.isDebug()) {
                Timber.i(
                    "ImapFolder.copyMessages: couldn't find remote folder '%s' for %s",
                    escapedDestinationFolderName,
                    logId,
                )
            }

            throw FolderNotFoundException(folder.serverId)
        }

        return try {
            val imapResponses = connection!!.executeCommandWithIdSet(
                Commands.UID_COPY,
                escapedDestinationFolderName,
                uids,
            )

            UidCopyResponse.parse(imapResponses)?.uidMapping
        } catch (ioe: IOException) {
            throw ioExceptionHandler(connection, ioe)
        }
    }

    @Throws(MessagingException::class)
    override fun moveMessages(messages: List<ImapMessage>, folder: ImapFolder): Map<String, String>? {
        if (messages.isEmpty()) {
            return null
        }

        val uidMapping = copyMessages(messages, folder)
        setFlags(messages, setOf(Flag.DELETED), true)

        return uidMapping
    }

    @Throws(MessagingException::class)
    private fun getRemoteMessageCount(criteria: String): Int {
        checkOpen()

        try {
            val command = String.format(Locale.US, "SEARCH 1:* %s", criteria)
            val responses = executeSimpleCommand(command)

            return responses.sumOf { response ->
                if (ImapResponseParser.equalsIgnoreCase(response[0], "SEARCH")) {
                    response.size - 1
                } else {
                    0
                }
            }
        } catch (ioe: IOException) {
            throw ioExceptionHandler(connection, ioe)
        }
    }

    @get:Throws(MessagingException::class)
    val unreadMessageCount: Int
        get() = getRemoteMessageCount("UNSEEN NOT DELETED")

    @get:Throws(MessagingException::class)
    val flaggedMessageCount: Int
        get() = getRemoteMessageCount("FLAGGED NOT DELETED")

    @get:Throws(MessagingException::class)
    internal val highestUid: Long
        get() = try {
            val responses = executeSimpleCommand("UID SEARCH *:*")
            val searchResponse = SearchResponse.parse(responses)

            extractHighestUid(searchResponse)
        } catch (e: NegativeImapResponseException) {
            -1L
        } catch (ioe: IOException) {
            throw ioExceptionHandler(connection, ioe)
        }

    private fun extractHighestUid(searchResponse: SearchResponse): Long {
        return searchResponse.numbers.maxOrNull() ?: -1L
    }

    override fun getMessage(uid: String): ImapMessage {
        return ImapMessage(uid)
    }

    @Throws(MessagingException::class)
    override fun getMessages(
        start: Int,
        end: Int,
        earliestDate: Date?,
        listener: MessageRetrievalListener<ImapMessage>?,
    ): List<ImapMessage> {
        return getMessages(start, end, earliestDate, false, listener)
    }

    @Throws(MessagingException::class)
    private fun getMessages(
        start: Int,
        end: Int,
        earliestDate: Date?,
        includeDeleted: Boolean,
        listener: MessageRetrievalListener<ImapMessage>?,
    ): List<ImapMessage> {
        if (start < 1 || end < 1 || end < start) {
            throw MessagingException(String.format(Locale.US, "Invalid message set %d %d", start, end))
        }

        checkOpen()

        val dateSearchString = getDateSearchString(earliestDate)
        val command = String.format(
            Locale.US,
            "UID SEARCH %d:%d%s%s",
            start,
            end,
            dateSearchString,
            if (includeDeleted) "" else " NOT DELETED",
        )

        try {
            val imapResponses = connection!!.executeSimpleCommand(command)
            val searchResponse = SearchResponse.parse(imapResponses)
            return getMessages(searchResponse, listener)
        } catch (ioe: IOException) {
            throw ioExceptionHandler(connection, ioe)
        }
    }

    private fun getDateSearchString(earliestDate: Date?): String {
        return if (earliestDate == null) {
            ""
        } else {
            " SINCE " + RFC3501_DATE.get()!!.format(earliestDate)
        }
    }

    @Throws(IOException::class, MessagingException::class)
    override fun areMoreMessagesAvailable(indexOfOldestMessage: Int, earliestDate: Date?): Boolean {
        checkOpen()

        if (indexOfOldestMessage == 1) {
            return false
        }

        var endIndex = indexOfOldestMessage - 1
        val dateSearchString = getDateSearchString(earliestDate)

        while (endIndex > 0) {
            val startIndex = max(0, endIndex - MORE_MESSAGES_WINDOW_SIZE) + 1
            if (existsNonDeletedMessageInRange(startIndex, endIndex, dateSearchString)) {
                return true
            }
            endIndex -= MORE_MESSAGES_WINDOW_SIZE
        }

        return false
    }

    @Throws(MessagingException::class, IOException::class)
    private fun existsNonDeletedMessageInRange(startIndex: Int, endIndex: Int, dateSearchString: String): Boolean {
        val command = String.format(
            Locale.US,
            "SEARCH %d:%d%s NOT DELETED",
            startIndex,
            endIndex,
            dateSearchString,
        )
        val imapResponses = executeSimpleCommand(command)

        val response = SearchResponse.parse(imapResponses)
        return response.numbers.size > 0
    }

    @Throws(MessagingException::class)
    internal fun getMessages(
        mesgSeqs: Set<Long>,
        includeDeleted: Boolean,
        listener: MessageRetrievalListener<ImapMessage>?,
    ): List<ImapMessage> {
        checkOpen()

        try {
            val commandSuffix = if (includeDeleted) "" else " NOT DELETED"
            val imapResponses = connection!!.executeCommandWithIdSet(Commands.UID_SEARCH, commandSuffix, mesgSeqs)

            val searchResponse = SearchResponse.parse(imapResponses)
            return getMessages(searchResponse, listener)
        } catch (ioe: IOException) {
            throw ioExceptionHandler(connection, ioe)
        }
    }

    @Throws(MessagingException::class)
    internal fun getMessagesFromUids(mesgUids: List<String>): List<ImapMessage> {
        checkOpen()

        val uidSet = mesgUids.map { it.toLong() }.toSet()

        try {
            val imapResponses = connection!!.executeCommandWithIdSet("UID SEARCH UID", "", uidSet)

            val searchResponse = SearchResponse.parse(imapResponses)
            return getMessages(searchResponse, null)
        } catch (ioe: IOException) {
            throw ioExceptionHandler(connection, ioe)
        }
    }

    private fun getMessages(
        searchResponse: SearchResponse,
        listener: MessageRetrievalListener<ImapMessage>?,
    ): List<ImapMessage> {
        // Sort the uids in numerically decreasing order
        // By doing it in decreasing order, we ensure newest messages are dealt with first
        // This makes the most sense when a limit is imposed, and also prevents UI from going
        // crazy adding stuff at the top.
        val uids = searchResponse.numbers.sortedDescending()

        return uids.map { uidLong ->
            val uid = uidLong.toString()
            val message = ImapMessage(uid)
            listener?.messageFinished(message)

            message
        }
    }

    @Throws(MessagingException::class)
    override fun fetch(
        messages: List<ImapMessage>,
        fetchProfile: FetchProfile,
        listener: FetchListener?,
        maxDownloadSize: Int,
    ) {
        if (messages.isEmpty()) {
            return
        }

        checkOpen()

        val messageMap = messages.associateBy { it.uid }
        val uids = messages.map { it.uid }

        val fetchFields: MutableSet<String> = LinkedHashSet()
        fetchFields.add("UID")
        if (fetchProfile.contains(FetchProfile.Item.FLAGS)) {
            fetchFields.add("FLAGS")
        }

        if (fetchProfile.contains(FetchProfile.Item.ENVELOPE)) {
            fetchFields.add("INTERNALDATE")
            fetchFields.add("RFC822.SIZE")
            fetchFields.add(
                "BODY.PEEK[HEADER.FIELDS (date subject from content-type to cc bcc " +
                    "reply-to message-id references in-reply-to list-post list-unsubscribe sender " +
                    K9MailLib.IDENTITY_HEADER + " " + K9MailLib.CHAT_HEADER + ")]",
            )
        }

        if (fetchProfile.contains(FetchProfile.Item.STRUCTURE)) {
            fetchFields.add("BODYSTRUCTURE")
        }

        if (fetchProfile.contains(FetchProfile.Item.BODY_SANE)) {
            if (maxDownloadSize > 0) {
                fetchFields.add(String.format(Locale.US, "BODY.PEEK[]<0.%d>", maxDownloadSize))
            } else {
                fetchFields.add("BODY.PEEK[]")
            }
        }

        if (fetchProfile.contains(FetchProfile.Item.BODY)) {
            fetchFields.add("BODY.PEEK[]")
        }

        val spaceSeparatedFetchFields = ImapUtility.join(" ", fetchFields)
        var windowStart = 0
        val processedUids = mutableSetOf<String>()
        while (windowStart < messages.size) {
            val windowEnd = min(windowStart + FETCH_WINDOW_SIZE, messages.size)
            val uidWindow = uids.subList(windowStart, windowEnd)

            try {
                val commaSeparatedUids = ImapUtility.join(",", uidWindow)
                val command = String.format("UID FETCH %s (%s)", commaSeparatedUids, spaceSeparatedFetchFields)
                connection!!.sendCommand(command, false)

                var callback: ImapResponseCallback? = null
                if (fetchProfile.contains(FetchProfile.Item.BODY) ||
                    fetchProfile.contains(FetchProfile.Item.BODY_SANE)
                ) {
                    callback = FetchBodyCallback(messageMap)
                }

                var response: ImapResponse
                do {
                    response = connection!!.readResponse(callback)
                    if (response.tag == null && ImapResponseParser.equalsIgnoreCase(response[1], "FETCH")) {
                        val fetchList = response.getKeyedValue("FETCH") as ImapList
                        val uid = fetchList.getKeyedString("UID")

                        val message = messageMap[uid]
                        if (message == null) {
                            if (K9MailLib.isDebug()) {
                                Timber.d("Do not have message in messageMap for UID %s for %s", uid, logId)
                            }
                            handleUntaggedResponse(response)
                            continue
                        }

                        val literal = handleFetchResponse(message, fetchList)
                        if (literal != null) {
                            when (literal) {
                                is String -> {
                                    val bodyStream: InputStream = literal.toByteArray().inputStream()
                                    message.parse(bodyStream)
                                }
                                is Int -> {
                                    // All the work was done in FetchBodyCallback.foundLiteral()
                                }
                                else -> {
                                    // This shouldn't happen
                                    throw MessagingException("Got FETCH response with bogus parameters")
                                }
                            }
                        }

                        val isFirstResponse = uid !in processedUids
                        processedUids.add(uid)

                        listener?.onFetchResponse(message, isFirstResponse)
                    } else {
                        handleUntaggedResponse(response)
                    }
                } while (response.tag == null)
            } catch (ioe: IOException) {
                throw ioExceptionHandler(connection, ioe)
            }

            windowStart += FETCH_WINDOW_SIZE
        }
    }

    @Throws(MessagingException::class)
    override fun fetchPart(
        message: ImapMessage,
        part: Part,
        bodyFactory: BodyFactory,
        maxDownloadSize: Int,
    ) {
        checkOpen()

        val partId = part.serverExtra

        val fetch = if ("TEXT".equals(partId, ignoreCase = true)) {
            String.format(Locale.US, "BODY.PEEK[TEXT]<0.%d>", maxDownloadSize)
        } else {
            String.format("BODY.PEEK[%s]", partId)
        }

        try {
            val command = String.format("UID FETCH %s (UID %s)", message.uid, fetch)
            connection!!.sendCommand(command, false)

            val callback: ImapResponseCallback = FetchPartCallback(part, bodyFactory)

            var response: ImapResponse
            do {
                response = connection!!.readResponse(callback)

                if (response.tag == null && ImapResponseParser.equalsIgnoreCase(response[1], "FETCH")) {
                    val fetchList = response.getKeyedValue("FETCH") as ImapList
                    val uid = fetchList.getKeyedString("UID")
                    if (message.uid != uid) {
                        if (K9MailLib.isDebug()) {
                            Timber.d("Did not ask for UID %s for %s", uid, logId)
                        }
                        handleUntaggedResponse(response)
                        continue
                    }

                    val literal = handleFetchResponse(message, fetchList)
                    if (literal != null) {
                        when (literal) {
                            is Body -> {
                                // Most of the work was done in FetchAttachmentCallback.foundLiteral()
                                MimeMessageHelper.setBody(part, literal as Body?)
                            }
                            is String -> {
                                val bodyStream: InputStream = literal.toByteArray().inputStream()
                                val contentTransferEncoding =
                                    part.getHeader(MimeHeader.HEADER_CONTENT_TRANSFER_ENCODING)[0]
                                val contentType = part.getHeader(MimeHeader.HEADER_CONTENT_TYPE)[0]
                                val body = bodyFactory.createBody(contentTransferEncoding, contentType, bodyStream)
                                MimeMessageHelper.setBody(part, body)
                            }
                            else -> {
                                // This shouldn't happen
                                throw MessagingException("Got FETCH response with bogus parameters")
                            }
                        }
                    }
                } else {
                    handleUntaggedResponse(response)
                }
            } while (response.tag == null)
        } catch (ioe: IOException) {
            throw ioExceptionHandler(connection, ioe)
        }
    }

    // Returns value of body field
    @Throws(MessagingException::class)
    private fun handleFetchResponse(message: ImapMessage, fetchList: ImapList): Any? {
        var result: Any? = null
        if (fetchList.containsKey("FLAGS")) {
            val flags = fetchList.getKeyedList("FLAGS")
            if (flags != null) {
                for (i in flags.indices) {
                    val flag = flags.getString(i)
                    when {
                        flag.equals("\\Deleted", ignoreCase = true) -> {
                            message.setFlag(Flag.DELETED, true)
                        }
                        flag.equals("\\Answered", ignoreCase = true) -> {
                            message.setFlag(Flag.ANSWERED, true)
                        }
                        flag.equals("\\Seen", ignoreCase = true) -> {
                            message.setFlag(Flag.SEEN, true)
                        }
                        flag.equals("\\Flagged", ignoreCase = true) -> {
                            message.setFlag(Flag.FLAGGED, true)
                        }
                        flag.equals("\$Forwarded", ignoreCase = true) -> {
                            message.setFlag(Flag.FORWARDED, true)
                            // a message contains FORWARDED FLAG -> so we can also create them
                            internalImapStore.getPermanentFlagsIndex().add(Flag.FORWARDED)
                        }
                        flag.equals("\\Draft", ignoreCase = true) -> {
                            message.setFlag(Flag.DRAFT, true)
                        }
                    }
                }
            }
        }

        if (fetchList.containsKey("INTERNALDATE")) {
            message.internalDate = fetchList.getKeyedDate("INTERNALDATE")
        }

        if (fetchList.containsKey("RFC822.SIZE")) {
            val size = fetchList.getKeyedNumber("RFC822.SIZE")
            message.setSize(size)
        }

        if (fetchList.containsKey("BODYSTRUCTURE")) {
            val bs = fetchList.getKeyedList("BODYSTRUCTURE")
            if (bs != null) {
                try {
                    parseBodyStructure(bs, message, "TEXT")
                } catch (e: MessagingException) {
                    if (K9MailLib.isDebug()) {
                        Timber.d(e, "Error handling message for %s", logId)
                    }
                    message.body = null
                }
            }
        }

        if (fetchList.containsKey("BODY")) {
            val index = fetchList.getKeyIndex("BODY") + 2
            val size = fetchList.size
            if (index < size) {
                result = fetchList.getObject(index)

                // Check if there's an origin octet
                if (result is String) {
                    if (result.startsWith("<") && index + 1 < size) {
                        result = fetchList.getObject(index + 1)
                    }
                }
            }
        }

        return result
    }

    private fun handleUntaggedResponses(responses: List<ImapResponse>): List<ImapResponse> {
        for (response in responses) {
            handleUntaggedResponse(response)
        }
        return responses
    }

    private fun handlePossibleUidNext(response: ImapResponse) {
        if (ImapResponseParser.equalsIgnoreCase(response[0], "OK") && response.size > 1) {
            val bracketed = response[1] as? ImapList ?: return
            val key = bracketed.firstOrNull() as? String ?: return
            if ("UIDNEXT".equals(key, ignoreCase = true)) {
                uidNext = bracketed.getLong(1)
                if (K9MailLib.isDebug()) {
                    Timber.d("Got UidNext = %s for %s", uidNext, logId)
                }
            }
        }
    }

    /**
     * Handle an untagged response that the caller doesn't care to handle themselves.
     */
    private fun handleUntaggedResponse(response: ImapResponse) {
        if (response.tag == null && response.size > 1) {
            if (ImapResponseParser.equalsIgnoreCase(response[1], "EXISTS")) {
                messageCount = response.getNumber(0)
                if (K9MailLib.isDebug()) {
                    Timber.d("Got untagged EXISTS with value %d for %s", messageCount, logId)
                }
            }

            handlePossibleUidNext(response)

            if (ImapResponseParser.equalsIgnoreCase(response[1], "EXPUNGE") && messageCount > 0) {
                messageCount--
                if (K9MailLib.isDebug()) {
                    Timber.d("Got untagged EXPUNGE with messageCount %d for %s", messageCount, logId)
                }
            }
        }
    }

    @Throws(MessagingException::class)
    private fun parseBodyStructure(bs: ImapList, part: Part, id: String) {
        if (bs[0] is ImapList) {
            // This is a multipart
            val mp = MimeMultipart.newInstance()
            for (i in bs.indices) {
                if (bs[i] is ImapList) {
                    // For each part in the message we're going to add a new BodyPart and parse into it.
                    val bp = MimeBodyPart()
                    val bodyPartId = (i + 1).toString()
                    if (id.equals("TEXT", ignoreCase = true)) {
                        parseBodyStructure(bs.getList(i), bp, bodyPartId)
                    } else {
                        parseBodyStructure(bs.getList(i), bp, "$id.$bodyPartId")
                    }
                    mp.addBodyPart(bp)
                } else {
                    // We've got to the end of the children of the part, so now we can find out what type it is and
                    // bail out.
                    val subType = bs.getString(i)
                    mp.setSubType(subType.lowercase())
                    break
                }
            }
            MimeMessageHelper.setBody(part, mp)
        } else {
            // This is a body. We need to add as much information as we can find out about it to the Part.

            /*
             *  0| 0  body type
             *  1| 1  body subtype
             *  2| 2  body parameter parenthesized list
             *  3| 3  body id (unused)
             *  4| 4  body description (unused)
             *  5| 5  body encoding
             *  6| 6  body size
             *  -| 7  text lines (only for type TEXT, unused)
             * Extensions (optional):
             *  7| 8  body MD5 (unused)
             *  8| 9  body disposition
             *  9|10  body language (unused)
             * 10|11  body location (unused)
             */
            val type = bs.getString(0)
            val subType = bs.getString(1)
            val mimeType = "$type/$subType".lowercase()

            var bodyParams: ImapList? = null
            if (bs[2] is ImapList) {
                bodyParams = bs.getList(2)
            }
            val encoding = bs.getString(5)
            val size = bs.getNumber(6)

            if (MimeUtility.isMessage(mimeType)) {
//                  A body type of type MESSAGE and subtype RFC822
//                  contains, immediately after the basic fields, the
//                  envelope structure, body structure, and size in
//                  text lines of the encapsulated message.
//                    [MESSAGE, RFC822, [NAME, Fwd: [#HTR-517941]:  update plans at 1am Friday - Memory allocation - displayware.eml], NIL, NIL, 7BIT, 5974, NIL, [INLINE, [FILENAME*0, Fwd: [#HTR-517941]:  update plans at 1am Friday - Memory all, FILENAME*1, ocation - displayware.eml]], NIL]
                /*
                 * This will be caught by fetch and handled appropriately.
                 */
                throw MessagingException("BODYSTRUCTURE message/rfc822 not yet supported.")
            }

            // Set the content type with as much information as we know right now.
            val contentType = StringBuilder()
            contentType.append(mimeType)

            if (bodyParams != null) {
                // If there are body params we might be able to get some more information out of them.
                for (i in bodyParams.indices step 2) {
                    val paramName = bodyParams.getString(i)
                    val paramValue = bodyParams.getString(i + 1)
                    val encodedValue = if (paramValue.isToken()) paramValue else paramValue.quotedUtf8()
                    contentType.append(String.format(";\r\n %s=%s", paramName, encodedValue))
                }
            }

            part.setHeader(MimeHeader.HEADER_CONTENT_TYPE, contentType.toString())

            // Extension items
            var bodyDisposition: ImapList? = null
            if ("text".equals(type, ignoreCase = true) && bs.size > 9 && bs[9] is ImapList) {
                bodyDisposition = bs.getList(9)
            } else if (!"text".equals(type, ignoreCase = true) && bs.size > 8 && bs[8] is ImapList) {
                bodyDisposition = bs.getList(8)
            }

            val contentDisposition = StringBuilder()
            if (bodyDisposition != null && !bodyDisposition.isEmpty()) {
                if (!"NIL".equals(bodyDisposition.getString(0), ignoreCase = true)) {
                    contentDisposition.append(bodyDisposition.getString(0).lowercase())
                }
                if (bodyDisposition.size > 1 && bodyDisposition[1] is ImapList) {
                    val bodyDispositionParams = bodyDisposition.getList(1)
                    // If there is body disposition information we can pull some more information
                    // about the attachment out.
                    for (i in bodyDispositionParams.indices step 2) {
                        val paramName = bodyDispositionParams.getString(i).lowercase()
                        val paramValue = bodyDispositionParams.getString(i + 1)
                        val encodedValue = if (paramValue.isToken()) paramValue else paramValue.quotedUtf8()
                        contentDisposition.append(String.format(";\r\n %s=%s", paramName, encodedValue))
                    }
                }
            }

            if (MimeUtility.getHeaderParameter(contentDisposition.toString(), "size") == null) {
                contentDisposition.append(String.format(Locale.US, ";\r\n size=%d", size))
            }

            // Set the content disposition containing at least the size. Attachment  handling code will use this
            // down the road.
            part.setHeader(MimeHeader.HEADER_CONTENT_DISPOSITION, contentDisposition.toString())

            // Set the Content-Transfer-Encoding header. Attachment code will use this to parse the body.
            part.setHeader(MimeHeader.HEADER_CONTENT_TRANSFER_ENCODING, encoding)

            if (part is ImapMessage) {
                part.setSize(size)
            }

            part.serverExtra = id
        }
    }

    /**
     * Appends the given messages to the selected folder.
     *
     * This implementation also determines the new UIDs of the given messages on the IMAP
     * server and changes the messages' UIDs to the new server UIDs.
     *
     * @param messages
     * The messages to append to the folder.
     *
     * @return The mapping of original message UIDs to the new server UIDs.
     */
    @Throws(MessagingException::class)
    override fun appendMessages(messages: List<Message>): Map<String, String>? {
        open(OpenMode.READ_WRITE)
        checkOpen()

        return try {
            val uidMap: MutableMap<String, String> = HashMap()
            for (message in messages) {
                val messageSize = message.calculateSize()

                val encodeFolderName = folderNameCodec.encode(prefixedName)
                val escapedFolderName = ImapUtility.encodeString(encodeFolderName)
                val combinedFlags = ImapUtility.combineFlags(
                    message.flags,
                    canCreateKeywords || internalImapStore.getPermanentFlagsIndex().contains(Flag.FORWARDED),
                )
                val command = String.format(
                    Locale.US,
                    "APPEND %s (%s) {%d}",
                    escapedFolderName,
                    combinedFlags,
                    messageSize,
                )
                connection!!.sendCommand(command, false)

                var response: ImapResponse
                do {
                    response = connection!!.readResponse()

                    handleUntaggedResponse(response)

                    if (response.isContinuationRequested) {
                        val eolOut = EOLConvertingOutputStream(connection!!.outputStream)
                        message.writeTo(eolOut)
                        eolOut.write('\r'.code)
                        eolOut.write('\n'.code)
                        eolOut.flush()
                    }
                } while (response.tag == null)

                if (response.size < 1 || !ImapResponseParser.equalsIgnoreCase(response[0], Responses.OK)) {
                    throw NegativeImapResponseException("APPEND failed", listOf(response))
                } else if (response.size > 1) {
                    /*
                     * If the server supports UIDPLUS, then along with the APPEND response it
                     * will return an APPENDUID response code, e.g.
                     *
                     * 11 OK [APPENDUID 2 238268] APPEND completed
                     *
                     * We can use the UID included in this response to update our records.
                     */
                    val appendList = response[1]
                    if (appendList is ImapList) {
                        if (appendList.size >= 3 && appendList.getString(0) == "APPENDUID") {
                            val newUid = appendList.getString(2)
                            if (newUid.isNotEmpty()) {
                                uidMap[message.uid] = newUid
                                message.uid = newUid
                                continue
                            }
                        }
                    }
                }

                // This part is executed in case the server does not support UIDPLUS or does not implement the
                // APPENDUID response code.
                val messageId = extractMessageId(message)
                val newUid = messageId?.let { getUidFromMessageId(it) }
                if (K9MailLib.isDebug()) {
                    Timber.d("Got UID %s for message for %s", newUid, logId)
                }

                newUid?.let {
                    uidMap[message.uid] = newUid
                    message.uid = newUid
                }
            }

            // We need uidMap to be null if new UIDs are not available to maintain consistency with the behavior of
            // other similar methods (copyMessages, moveMessages) which return null.
            if (uidMap.isEmpty()) null else uidMap
        } catch (ioe: IOException) {
            throw ioExceptionHandler(connection, ioe)
        }
    }

    private fun extractMessageId(message: Message): String? {
        return message.getHeader("Message-ID").firstOrNull()
    }

    @Throws(MessagingException::class)
    override fun getUidFromMessageId(messageId: String): String? {
        if (K9MailLib.isDebug()) {
            Timber.d("Looking for UID for message with message-id %s for %s", messageId, logId)
        }

        val command = String.format("UID SEARCH HEADER MESSAGE-ID %s", ImapUtility.encodeString(messageId))
        val imapResponses = try {
            executeSimpleCommand(command)
        } catch (ioe: IOException) {
            throw ioExceptionHandler(connection, ioe)
        }

        val searchResponse = SearchResponse.parse(imapResponses)
        return searchResponse.numbers.firstOrNull()?.toString()
    }

    @Throws(MessagingException::class)
    override fun expunge() {
        open(OpenMode.READ_WRITE)
        checkOpen()

        try {
            executeSimpleCommand("EXPUNGE")
        } catch (ioe: IOException) {
            throw ioExceptionHandler(connection, ioe)
        }
    }

    @Throws(MessagingException::class)
    override fun expungeUids(uids: List<String>) {
        require(uids.isNotEmpty()) { "expungeUids() must be called with a non-empty set of UIDs" }

        open(OpenMode.READ_WRITE)
        checkOpen()

        try {
            if (connection!!.isUidPlusCapable) {
                val longUids = uids.map { it.toLong() }.toSet()
                connection!!.executeCommandWithIdSet(Commands.UID_EXPUNGE, "", longUids)
            } else {
                executeSimpleCommand("EXPUNGE")
            }
        } catch (ioe: IOException) {
            throw ioExceptionHandler(connection, ioe)
        }
    }

    @Throws(MessagingException::class)
    override fun setFlags(flags: Set<Flag>, value: Boolean) {
        open(OpenMode.READ_WRITE)
        checkOpen()

        val canCreateForwardedFlag = canCreateKeywords || internalImapStore.getPermanentFlagsIndex().contains(Flag.FORWARDED)
        try {
            val combinedFlags = ImapUtility.combineFlags(flags, canCreateForwardedFlag)
            val command = String.format(
                "%s 1:* %sFLAGS.SILENT (%s)",
                Commands.UID_STORE,
                if (value) "+" else "-",
                combinedFlags,
            )

            executeSimpleCommand(command)
        } catch (ioe: IOException) {
            throw ioExceptionHandler(connection, ioe)
        }
    }

    @Throws(MessagingException::class)
    override fun setFlags(messages: List<ImapMessage>, flags: Set<Flag>, value: Boolean) {
        open(OpenMode.READ_WRITE)
        checkOpen()

        val uids = messages.map { it.uid.toLong() }.toSet()
        val canCreateForwardedFlag = canCreateKeywords || internalImapStore.getPermanentFlagsIndex().contains(Flag.FORWARDED)
        val combinedFlags = ImapUtility.combineFlags(flags, canCreateForwardedFlag)
        val commandSuffix = String.format("%sFLAGS.SILENT (%s)", if (value) "+" else "-", combinedFlags)
        try {
            connection!!.executeCommandWithIdSet(Commands.UID_STORE, commandSuffix, uids)
        } catch (ioe: IOException) {
            throw ioExceptionHandler(connection, ioe)
        }
    }

    @Throws(MessagingException::class)
    private fun checkOpen() {
        if (!isOpen) {
            throw MessagingException("Folder $prefixedName is not open.")
        }
    }

    private fun ioExceptionHandler(connection: ImapConnection?, ioe: IOException): MessagingException {
        Timber.e(ioe, "IOException for %s", logId)
        connection?.close()
        close()
        return MessagingException("IO Error", ioe)
    }

    override fun equals(other: Any?): Boolean {
        if (other is ImapFolder) {
            return other.serverId == serverId
        }
        return super.equals(other)
    }

    override fun hashCode(): Int {
        return serverId.hashCode()
    }

    private val logId: String
        get() {
            var id = internalImapStore.logLabel + ":" + serverId + "/" + Thread.currentThread().name
            if (connection != null) {
                id += "/" + connection!!.logId
            }
            return id
        }

    /**
     * Search the remote ImapFolder.
     */
    @Throws(MessagingException::class)
    override fun search(
        queryString: String?,
        requiredFlags: Set<Flag>?,
        forbiddenFlags: Set<Flag>?,
        performFullTextSearch: Boolean,
    ): List<ImapMessage> {
        try {
            open(OpenMode.READ_ONLY)
            checkOpen()

            inSearch = true

            val searchCommand = UidSearchCommandBuilder()
                .queryString(queryString)
                .performFullTextSearch(performFullTextSearch)
                .requiredFlags(requiredFlags)
                .forbiddenFlags(forbiddenFlags)
                .build()

            try {
                val imapResponses = executeSimpleCommand(searchCommand)
                val searchResponse = SearchResponse.parse(imapResponses)

                return getMessages(searchResponse, null)
            } catch (ioe: IOException) {
                throw ioExceptionHandler(connection, ioe)
            }
        } finally {
            inSearch = false
        }
    }

    companion object {
        private const val MORE_MESSAGES_WINDOW_SIZE = 500
        private const val FETCH_WINDOW_SIZE = 100

        const val INBOX = "INBOX"

        private val RFC3501_DATE: ThreadLocal<SimpleDateFormat> = object : ThreadLocal<SimpleDateFormat>() {
            override fun initialValue(): SimpleDateFormat {
                return SimpleDateFormat("dd-MMM-yyyy", Locale.US)
            }
        }
    }
}

enum class OpenMode {
    READ_WRITE,
    READ_ONLY,
}
